$ { {-5} \times \left[\begin{array}{r}{-2} \\ {3} \\ {4}\end{array}\right] = {?} } $
Explanation: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{r}{-5}\times{-2} \\ {-5}\times{3} \\ {-5}\times{4}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{r}{10} \\ {-15} \\ {-20}\end{array}\right]}$